Dungeon Samurai book 2. Serious spoilers ahead.
It opens with Yamada in the forest -- such as it is. Every tree exactly the same distance from another, no fallen trees, no birdsongs. . . .
Mole men attack. And what's worse, one has a skill like the dungeon samurai's.
The first of many complications in their lives. Evolving skills on their side. Discovery of new monsters as they delve deeper into the dungeon. Boss fights. The need to summon more people. Leadership. Technology. And more.